Moscow (AFP) – A Russian court on Sunday ordered a Greenpeace spokesman to be detained for two months over an open-sea protest against Arctic oil drilling, in a criminal case that has caused international concern.

The court in the northern city of Murmansk on Thursday had already ordered the two-month detention of 22 Greenpeace activists pending the investigation into alleged piracy over a protest at a Gazprom oil rig on September 18.

The same Lenin district court had also remanded in custody eight activists for 72 hours until a new hearing on Sunday.

The judge has ordered the first of those eight activists, Dmitri Litvinov, a Greenpeace spokesman and a Swedish-American dual citizen of Russian origin, to also remain in pre-trial detention for two months.

During the hearing the bespectacled great-grandson of Maxim Litvinov, a Soviet foreign minister under Josef Stalin, stood in a metal cage in the courtroom wearing a baseball cap, live footage showed.

The court was on Sunday set to hold simultaneous hearings in several different courtrooms to decide whether to extend the detention for the other seven Greenpeace activists and crew members.

The total of 30 detained crew members of Greenpeace's Dutch-flagged Arctic Sunrise icebreaker include six British citizens, four Russians and nationals of 16 other countries including Argentina, Italy, France and Australia.

Russian investigators have accused the Greenpeace activists of piracy after two of them tried to scale state energy giant Gazprom's Prirazlomnaya oil platform in the Barents Sea.

The group has denied committing piracy and accuses Russia of illegally boarding its ship in international waters.

Russian President Vladimir Putin has said that the activists "are of course not pirates" but stressed they had broken international law by getting dangerously close to the oil rig.

Charges of piracy carry a maximum prison term of 15 years but the Investigative Committee said that the charge against the group could be reduced in the course of the probe.

Among those detained for two months are the vessel's captain, Peter Willcox, who was also the captain of Greenpeace's Rainbow Warrior ship, which French secret services bombed and sunk in New Zealand in 1985.

Another is photographer Denis Sinyakov, a former staff photographer at AFP and Reuters who was working for Greenpeace as a freelancer.

In protest at his detention, several Russian news websites including that of national television channel NTV blacked out their photographs on Friday.

The Netherlands government called on Moscow to immediately release the detained activists and said it was considering legal action.

The arrests also sparked outrage from Russian and international rights activists, with Reporters Without Borders saying Russian investigators were "criminalising both journalists and environmental activists."